False keels..

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1 February 2014 at 07:48 #46766
Richard J Huggett
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@richardjhuggett
I've ordered another Tamiya USS Enterprise carrier, I made a right cock of the first one, I put far too much stuff in it, and it ended up so unstable I couldn't use it, it even fell over in the bath.

I don't want to do that again, so this one is set to have a false keel fitted. I'm thinking of making a perspex keel, similar to those big old fashioned yachts had fitted to them…maybe half the keel length or so, and a couple of inches deep, cutting a slot in the hull and pinning and glueing it in place.

But before I do, any more suggestions, chaps?
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1 February 2014 at 07:48 #4074
Richard J Huggett
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@richardjhuggett
1 February 2014 at 13:18 #46772
Paul T
Participant
@pault84577
Hello Richard

Is the proposed keel simply for lateral stability or is the intention to create low down weight and get some mass below the waterline?

Paul
1 February 2014 at 13:38 #46773
Richard J Huggett
Participant
@richardjhuggett
Hi Paul,

Mainly for stability, I can mount the radio gear as low as possible(on the hull floor)it's really to try and stop it falling over like the last one did. Mind you, the last one was jammed full of 'stuff'…mP3 player, amp, speaker, lights, mixer for the esc's etc…this one won't be, I've learned a lesson from that.

Richard
1 February 2014 at 14:04 #46775
Paul T
Participant
@pault84577
Richard

A large keel might make the model difficult to steer, you could opt for a bulb type keel i.e. a bulb shape weight on the bottom of a thin section keel (a bit like a small torpedo on the bottom of a 6in school ruler) this would provide some low down weight for stability without compromising the models manoeuvrability.

Paul
1 February 2014 at 14:06 #46776
ashley needham
Participant
@ashleyneedham69188
Richard. Cant see a problem with that. The only thing against too long a keel is it will impair turning performance, but with an aircraft carrier this is not so much of an issue.

Ashley
1 February 2014 at 14:22 #46779
Richard J Huggett
Participant
@richardjhuggett
Interesting, gentlemen…many thanks for the replies. I confess to not having considered the steering issues with the false keel fitted. As Ashley says though, it won't be that much of a problem with a carrier, and I don't want it to be able to turn on a sixpence.

But, the bulb idea sounds good Paul…bomb shaped fishing weights are readily available on eBay, and I'm sure if I asked nicely, the grandchildren would donate an old six inch ruler.

Thanks guys, plenty of food for thought there..

Richard
3 February 2014 at 07:56 #46830
Richard J Huggett
Participant
@richardjhuggett
Re the false keel question, I'm going to go with the fishing weight/plastic keel idea. That in itself raises two more questions :

(a) whereabouts would be the best place to mount the keel?
(b) and how heavy should the weight be?

(c) and how long should the fin be?

That's three questions…ooops!

I guess the fin would be placed at the boat's c of g? As for length of fin, I guess start at…say…6" and go from there? And the weight…if I start at 6 ounces, does that sound about right? Or is that a bit too heavy?

I'm going to make what I think is called a 'fin box' to allow me to slide the fin into a box fixed into the hull, and secured by an 'R' clip passing through the box and the fin, that makes for easy installation of the fin, and allows me to remove it when the boat is on display.

Apologies for the early morning brain teasers…

Richard
3 February 2014 at 10:24 #46839
ashley needham
Participant
@ashleyneedham69188
Richard. The weight is easy..float the carrier loaded with whatever you are putting in it, and see how much extra weight is required to bring it to the correct waterline..that will be the keel weight.

As to how long..trial and error. it will be easy enough to make a , say, foot long strip with holes at half inch intervals up it and just go sailing, adjusting the depth until you get the sort of result you want, with I would say preferably the minimum depth. The dagger board box will make that very easy.

C of G it has to be for safeties sake..again, I might try it out first (tape everything up and place the gear in the approximate position)and then cut the slot when you have a bit of an idea as to roughly where the keel needs to go.

Ashley
3 February 2014 at 11:12 #46844
Richard J Huggett
Participant
@richardjhuggett
That's exactly what I needed to know, thanks Ashley…much appreciated.

Richard
3 February 2014 at 14:35 #46848
Paul T
Participant
@pault84577
Richard

As a general rule of thumb the basic length of the extended keel should equal the height measured from the bottom of the hull to the top of the main superstructure, not including masts etc.

Paul
3 February 2014 at 14:47 #46850
Richard J Huggett
Participant
@richardjhuggett
Now there's something I didn't know…thanks Paul, much appreciated.

Richard
3 February 2014 at 15:59 #46852
Kimosubby Shipyards
Participant
@kimosubbyshipyards
Hi Richard,

just a few ideas. The first, for a round bottomed hull (the Bounty) I just filled some copper pipe with lead and bolted that to the lower, outer hull. Works fine.

HMS Chatham, below, built by one of our chaps had a severe stability problem, overcome by bolting on a "marblehead" ballast with added fins when sailing, though after all the drilling out the 3.6Kg is probably nearer 2Kg.

When on display the keel quickly unbolts from captive nuts inside the hull.

And on this monster [Deans Marine Celestine], stability came in the form of high voltage copper bus-bars again bolted through the hull into captive nuts. The bars also impart a leeway keel effect enabling very good manoeuvrability for this boat. At 6 foot she needed it

You can see the doubled bars between the two supports.

Kimmo

Edited By Kimosubby Shipyards on 03/02/2014 16:01:21
3 February 2014 at 16:34 #46856
Richard J Huggett
Participant
@richardjhuggett
Thanks Kimmo, the Marblhead keel idea sounds interesting, similar to what I have in mind. A friend of mine suggested using a steel bar running two thirds of the boat's length, once fixed and faired in it could stay there permanently.

I need sit down tonight with a large scotch, weigh up the pro's and con's of these ideas, then decide which one to go for.

Many thanks gents…as always, much appreciated.

Richard
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